LeetCode 15: 3sum — Step-by-Step Visual Trace

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Learn to solve the 3sum problem on LeetCode by finding unique triplets in an array that sum to zero

intermediate Published 9 Apr 2026
Action Steps
  1. Read the problem statement carefully to understand the requirements
  2. Initialize an empty list to store the result
  3. Sort the input array to apply the two-pointer technique
  4. Iterate over the array and use two pointers to find a pair that sums to the negation of the current element
  5. Apply the skipping duplicates technique to avoid duplicate triplets
  6. Return the list of unique triplets that sum to zero
Who Needs to Know This

Software engineers and developers can benefit from this lesson to improve their problem-solving skills and prepare for technical interviews

Key Insight

💡 Sorting the array and using the two-pointer technique can efficiently find unique triplets that sum to zero

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🚀 Solve 3sum on LeetCode by finding unique triplets that sum to zero! 💡

Full Article

Find all unique triplets in an array that sum to zero. Each triplet must contain three distinct elements and no duplicate triplets should be returned.
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